1. Field of the Invention
This invention relates to disk drives and personal computers, and more specifically to a shock mounting for a hard disk drive in a portable computer.
2. Description of the Prior Art
Personal computers are well known, as are portable personal computers, hereinafter referred to as portable computers. Most portable computers now sold include a hard drive disk drive (Winchester disk drive). A typical xe2x80x9cform factorxe2x80x9d for hard disk drives currently used in portable computers is two and a half inches, meaning the nominal diameter of the disk is two and a half inches. The typical overall size of such a hard disk drive is approximately four inches by three inches by one-half inch. In a portable computer, the hard disk drive is usually the component most sensitive to shock and vibration since it is the only rotating component, and it is mechanically complex. In use, the disk in the hard disk drive rotates at a high speed and a read/write head rides very closely above the disk. The head/disk arrangement is very sensitive to both vibration and shock and is easily damaged by either.
A typical shock parameter for a portable computer is that the portable computer can be dropped six inches onto a hard surface (e.g. table top) and that the hard disk drive itself sustains a maximum of 100G acceleration. It is to be understood that the hard disk drive itself is mounted within some sort of housing, typically metal and/or plastic, which is attached to the chassis of the portable computer.
To limit the shock to the hard disk drive to 100G, a typical prior art solution is to swathe the entire hard disk drive in a thick layer of very soft (polymer gel) material. This has the advantage of providing shock protection due to the softness of the material, and also eliminating transmission of vibration to the hard disk drive since gel dampens vibration. While effective, this approach has the drawback that the polymer gel material must be fairly thick, e.g. xe2x85x9c inch thick or more. This is a significant problem, especially with the smaller types of portable computers where internal volume is at a premium. In this case, the shock mounting material undesirably occupies more volume than does the hard disk drive itself inside the computer.
Also, of course, such shock mounting material is typically thermally insulative. This may be a problem since the hard disk drive includes a rotational drive motor and a head motor which generate heat which must be dissipated. Hence, this prior art solution, while effective in terms of shock and vibration isolation, is far from ideal in terms of portable computer system design. An improved shock mounting system which would be highly desirable would consume less volume and also not be thermally insulative.
In accordance with this invention, a hard disk drive is shock mounted within a housing in a portable computer. The shock mounting is a number of thin shock pads each having a small surface area. The shock pads are e.g. one or two millimeters thick, typically no more than five millimeters thick. Each shock pad is a shock absorbing material such as a viscoelastic polymer. The shock pads are collectively fairly small in surface area, e.g. 20% or less of the total surface area of the main top and bottom surfaces of the hard disk drive are covered by the shock pads. Most of the space between the outer surface of the hard disk drive and the inner surface of the housing is empty, or it may be used in one embodiment for installation of thermally conductive pads to provide an efficient heat path between the hard disk drive and e.g. the housing for heat dissipation.
These shock pads provide optimum shock and vibration isolation compared to that in the prior art, but occupy only an insignificant amount of volume since the shock pads are thin. The actual surface area of the shock pads and their thickness is determined so as to provide sufficient shock isolation while also minimizing amplification of resonant frequency vibrations to the hard disk drive from the portable computer.
Hence, the actual thickness and surface area of the shock mount is dependent upon the size and mass of the hard disk drive, as well as any resonant frequencies from which the hard disk drive must be protected.
This shock mounting is compatible with the usual sorts of housings for hard disk drives. For instance, in one embodiment the housing is a rigid box consisting of a bottom tray portion and a covering lid portion in which the hard disk drive fits. The shock mount pads are disposed between the inner surface of the housing and the outer surface of the hard disk drive. This housing in turn slides inside the portable computer on rails which are mounted on the portable computer chassis.
In another embodiment, the housing tray is mounted inside the portable computer on the chassis. The hard disk drive fits inside the tray and is isolated therefrom by shock pads. A cover fits over the hard disk drive and is also isolated from the hard disk drive by additional pads. This cover in turn is part of an outer surface of the portable computer. Of course, other types of housing are compatible with the present shock pad structure.
Also, while the presently disclosed shock mounting is directed to a hard disk drive, it is not so limited. As will be readily understood by one skilled in the art, in addition to hard disk drive, this scheme may be used with a floppy disk drive or with other types of disk drives. Of course, in the floppy disk (or other replaceable disk) drive embodiment, the front surface of the disk drive must be exposed through the outer housing of the portable computer. Otherwise the structures and methods disclosed herein for shock mounting are applicable to other than hard disk drives and also are not limited to the portable computer environment.